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Jan. 20, 2012 -- People who eat more foods rich in the mineral magnesium appear to reduce their odds of having a stroke, a new study shows.

The link between magnesium in the diet and stroke risk was strongest for ischemic stroke, which is when a clot blocks a blood vessel in the brain.

Researchers found that the risk for ischemic stroke, the most common type of stroke in older people, was reduced by 9% for each additional 100 milligrams of magnesium a person consumed each day.

Regularly eating magnesium-rich foods also helped modestly reduce the chances of having any type of stroke. The study found that for every 100 additional milligrams of magnesium per day, people cut their risk of stroke by 8%.

The best natural sources for the mineral are whole grain products, green leafy vegetables, nuts, and beans. Foods that supply close to 100 milligrams of magnesium a day include one ounce of almonds or cashews, one cup of beans or brown rice, three-quarters of a cup of cooked spinach, or one cup of cooked oat bran cereal.

The study appears in the February issue of The American Journal of Clinical Nutrition.

How Magnesium Affects Stroke

For the research, Swedish scientists from the Karolinska Institute reviewed data from seven previously published studies of magnesium intake and stroke. These studies were done between 1998 and 2011, and included more than 240,000 people.

In these studies, people aged 34 and older were followed from eight to 15 years. During that time, nearly 6,500 people had a stroke. The average magnesium intake of all study participants ranged from 242 milligrams a day up to 471 milligrams daily.

In the U.S., the Recommended Dietary Allowance for magnesium is 420 milligrams a day for men aged 31 and older, and 320 milligrams daily for women in the same age range.

The research showed that people who had higher amounts of magnesium in their diets had a lower risk for stroke. This was true even when the scientists took into account multiple other factors that may have confounded the results, such as blood pressure, diabetes, age, smoking, high cholesterol, physical activity, vitamin supplementation, other dietary factors, alcohol consumption, and family history of heart disease.

It's still unclear exactly how magnesium reduces stroke risk. The researchers suggest that the mineral's benefits may be related to its ability to lower blood pressure. Diets high in magnesium have also been linked with lower rates of type 2 diabetes, a risk factor for stroke.

"Although it is premature to recommend magnesium supplementation to reduce risk of stroke, increased consumption of magnesium-rich foods such as green leafy vegetables, beans, nuts, and whole-grain cereals appears to be prudent," the study researchers write.

An editorial on the study also encourages people at high risk for stroke to include more high-magnesium foods in their diets. And it suggests that it's time for a large study to test whether taking magnesium supplements can help prevent stroke and heart disease in adults at high risk for these health problems.

SOURCES:Larsson, S. American Journal of Clinical Nutrition, February 2012.Song, Y. American Journal of Clinical Nutrition, February 2012.Magnesium: Dietary Supplement Fact Sheet, Office of Dietary Supplements, National Institutes of Health.